"Pioneer's new PLX-1000 is not only a worthy successor to the legendary Technics SL-1200MK2, it is a serious contender for the best audiophile-grade turntable for less than $2000. Unabashedly recommended."
https://www.stereophile.com/content/gramophone-dreams-4-page-2
I don't know anything about the OP's TT-1520, whether it's an OEM or a Super OEM or something else entirely, but I would happily accept oldman54's appraisal that it's a decent turntable when used with a cartridge that doesn't require super light tracking forces.
It was good to hear that your AT3600L is tracking cleanly at 2.5 grams for you. That is really not excessive for its conical stylus, and don't be afraid to experiment with even higher tracking forces to see if that might give even better tracking with some records. Mistracking presents a greater risk for record damage than does somewhat heavier tracking forces.
The AT3600L's recommended tracking force varies with the source: LP Gear says 2.5-3.5 grams, Music Hall says 3-4 grams (with 3 grams being their recommendation), and the only source I've seen directly from AT said 2.5-4.5 grams. I track mine at 3.5 grams, as did a friend of mine after experimenting with his Music Hall turntable; the AT rep I spoke with on the phone said their recommendation was 3.5 grams.
The AT3600L body can also accept ATN91 and ATN91R replacement styli, both of which have a lower 1.5-2.5 gram recommended vtf range, which still includes the sweet spot oldman54 mentioned for your tone arm. My friend with the Music Hall turntable ended up preferring the ATN91R, tracking it at 2.25 grams.